Now we know one of Ghostface’s weaknesses: ornithophobia, or fear of birds. Fox’s tropical-bird cartoon Rio trounced the horror sequel Scream 4 and soared to a $40 million opening, according to studio estimates. That gives Rio the best opening weekend so far this year, beating Rango’s $38.1 million debut. It also represents another victory for Blue Sky Studios, which has produced such animated hits as Dr. Seuss’ Horton Hears a Who and the Ice Age movies. Rio, a Brazil-set adventure about the world’s last two blue macaws (voiced by Jesse Eisenberg and Anne Hathaway), earned 58 percent of its tally from 3-D theaters. The well-reviewed $90 million movie also received an “A” rating from CinemaScore audiences, which bodes well for its staying power over the next few weeks.

Scream 4, the first movie in the horror series in 11 years, had to settle for second place with a disappointing $19.3 million. For any other $40 million horror film, that result would be viewed as a decent start, but most industry experts were expecting much more from the Wes Craven project. The Dimension Films release fell far short of the debuts of Scream 2 ($32.9 million) and Scream 3 ($34.7 million), and well behind projections heading into the weekend. The film will almost certainly finish its run as the lowest-grossing entry in the franchise. Scream 4 apparently had trouble attracting new young fans, as only 54 percent of its audience was under the age of 25 – a low figure for a horror film. And the film’s R rating meant that younger teenagers had to get their scares from the PG-13 Insidious instead. CinemaScore moviegoers gave Scream 4 a mediocre “B-” grade.

The rest of the top five consisted of holdovers. The Easter Bunny comedy Hop, which had topped the box office the last two weeks, dropped to third place with $11.2 million – a 48 percent decline. In fourth was the surfing biopic Soul Surfer, which slipped only 30 percent for $7.4 million. And the teenage-assassin thriller Hanna dropped 41 percent for $7.3 million.

In semi-wide release, Robert Redford’s new historical drama The Conspirator, about the trial of Mary Surratt (Robin Wright) following the assassination of President Abraham Lincoln, collected a sturdy $3.9 million from 707 locations. And the Ayn Rand adaptation Atlas Shrugged: Part I debuted to a decent $1.7 million from 300 theaters. John Aglialoro, the Cybex fitness equipment CEO who financed the $10 million movie, spent nearly 20 years bringing Rand’s Objectivist novel to the big screen.

Check back next week as the best-selling-novel adaptation Water for Elephants, the comedy Tyler Perry’s Madea’s Big Happy Family, and the nature documentary African Cats attempt to wipe that smirk off of Rio’s feathery face.